I'm in the level inside the mountain after you take the elevator up to the ammunition room. I keep running into areas where I keep falling through the floors. Huge glitch, but I haven't heard anyone else complaining. Anyone else have this problem?

I was just wondering if anyone else had problems falling through the floor in the cave level? Before you catch the train. I would just fall to my death through the map. My only way to complete the level was to walk along the conveyor belts, stairs and anything that wasn't a floor texture. In other levels I also fell through rocks and floors of houses.